Watts to Kilowatt-Hours (kWh) Electrical Conversion Calculator

Convert watts to kilowatt-hours by entering power in watts and time in hours.

How to Convert Watts to Kilowatt-Hours

A kilowatt-hour, expressed as kWh or kW·h, is a measure of energy that is equivalent to 1,000 watts of power for a 1-hour time period. Thus, to convert watts to kilowatt-hours, multiply the power in watts by the number of hours, then divide by 1,000.

Use the following formula to calculate kWh:

kWh = (watts × hrs) ÷ 1,000

For example: let’s find the kWh of 1,500 watts for 2.5 hours.

kWh = (1,500 × 2.5) ÷ 1,000
kWh = 3,750 ÷ 1,000
kWh = 3.75

Electricity usage is often measured in watt-hours or kilowatt-hours, so if you can convert watts to kWh then you can predict how much an electric appliance might cost, or how much energy is required to power it.

For example: let’s predict how much it costs to power a light bulb every hour. A 100 watt light bulb uses 100 watts of power. To convert the power in watts to kilowatt-hours, multiply 100 watts by 1 hour, then divide by 1,000 to find the energy usage in kWh.

Energy = (100 × 1) ÷ 1,000
Energy = 100 ÷ 1,000
Energy = 0.1 kWh

If electricity costs $0.12 per kWh, then a 100 watt light bulb will cost 1.2 cents per hour that it’s on.

Try our electricity cost calculator to estimate the cost of power usage on your monthly bill.

Common Watts to Kilowatt-Hour Conversions

Common watts to kilowatt-hour conversions for a 1-hour time period, along with the estimated cost of electricity assuming a price of $0.12 per kWh.
Power in Watts Energy in Kilowatt-hours Electricity Cost
100 W 0.1 kWh $0.012 per hr
200 W 0.2 kWh $0.024 per hr
300 W 0.3 kWh $0.036 per hr
400 W 0.4 kWh $0.048 per hr
500 W 0.5 kWh $0.060 per hr
600 W 0.6 kWh $0.072 per hr
700 W 0.7 kWh $0.084 per hr
800 W 0.8 kWh $0.096 per hr
900 W 0.9 kWh $0.108 per hr
1000 W 1 kWh $0.112 per hr

Need to convert to watts? Use our kWh to watts conversion calculator.